| Abstract: | Orexins, hypothalamic neuropeptieds, are involved in modulation of food intake and arousal state. To examine further physiological roles of orexin in brain function, the effects of centrally administered orexin- A on body temperature was investigated in rats. Assessed by a telemetry-sensor system implanted into the abdominal cavity, infusion of orexin-A into the third cerebroventricle increased body temperature in a dose-responsive manner. Cumulative ambulatory activity was concomitantly increased during 6 h but not 12 h after administration of orexin-A. Expression of uncoupling protein 1 (UCP1) mRNA in brown adipose tissue, as a marker for peripheal thermogenesis which affects body temperature, failed to increase after orexin-A administration. Expression of UCP3 mRNA in skeletal muscle but not UCP 2 in white adipose tissue was upregulated by infusion of orexin-A. The resulting information indicates that orexin neuron regulates body temperature in coordination with control of arousal system independently of peripheral thermogenesis through the BAT UCP1. |
